The marine benthic red algae of Motupore Island and vicinity in the Port Moresby area (Papua New Guinea) are documented and 36 of the 161 species are illustrated. All records are listed with bibliographic, biogeographic, taxonomic and nomenclatural comments. The discovery of the east Australian species Gracilaria rhodymenioides represents a substantial range extension as does Ceramium lentiforme from New South Wales (Australia). One species of Gibsmithia also represents a significant range Show moreThe marine benthic red algae of Motupore Island and vicinity in the Port Moresby area (Papua New Guinea) are documented and 36 of the 161 species are illustrated. All records are listed with bibliographic, biogeographic, taxonomic and nomenclatural comments. The discovery of the east Australian species Gracilaria rhodymenioides represents a substantial range extension as does Ceramium lentiforme from New South Wales (Australia). One species of Gibsmithia also represents a significant range extension from its Lord Howe Island, Norfolk Island and southern Great Barrier Reef distributions. Forty-four species appear to be newly recorded for the Papua New Guinea marine flora and 108 are new records for Motupore Island. Because all collections were taken during the month of July, many seasonal entities may be missing from the list presented and the total marine flora are not yet known. Show less